[Xantier]

I've been doing few projects with it and find it very lovely. Interop with Java works flawlessly in my experiences and RxKotlin extending RxJava makes that side work nicely as well. For one project[0] I used Ratpack as the web tier and that with Guice locked in place very easily. DB side of things I have used Kotlinquery which did its job nicely for my small use case.

In another I used Spring Boot where Kotlin felt like a native in that environment.

I'm guessing if you are building something with ORMs or similar where Java Bean convention is needed, you might lack the beauty of immutability and data classes (there are workarounds though) but other than that most pieces drop in place without a hitch.

0: https://github.com/Xantier/trycatch